Short answer: match the coil to how cluttered your ground is. A small coil (Garrett draws the line at 6 inches; in practice the smallest coils for current detectors are 6-inch rounds like the Minelab EQX 06 and 8 x 5 inch ellipticals like the V8X) separates close targets and fits between roots, rocks and fences. A medium 8 to 11 inch coil is the general-purpose default, and most detectors ship with one. A large coil (over 11 inches, such as Minelab’s 15 x 12 inch EQX 15 or Nokta’s 13.5 x 12.5 inch LG35) covers more ground per sweep and reaches deeper on larger targets. The trade-offs are weight, poorer separation in trash and, says Minelab, more sensitivity to ground mineralization.

Garrett’s rule of thumb is that a coil detects a coin-sized object to roughly its own diameter. The same guide warns that above about 15 inches the field becomes less concentrated and starts to miss small objects.

This page summarizes manufacturer guidance and published coil specs. Metal Detecting Review has not measured depth or separation with any of these coils.

What the manufacturers say

Coil size Garrett guidance Minelab guidance
Small (under 6 in) Concentrated field; best around a lot of metal debris, in tight places and for very small objects; needs more sweeps to cover ground “V8X, EQX 06, or M8 are perfect for separating valuable targets from unwanted iron”
Medium (6 to 11 in) Best general-purpose choice for coins and coin-sized targets (8 to 9 in); lightweight and easy to maneuver V10X, EQX 11 or M11 “provide a good balance of coverage and depth”
Large (over 11 in) Wider, deeper field and fewer sweeps; can pick up several targets at once in trash; best for large, deeply buried targets Reach greater depths for large, long-buried objects, “may have reduced sensitivity to small targets and be more affected by ground mineralization”

Coil shape matters too. Garrett says an elliptical coil is more maneuverable and, because of its length, covers more ground than a round coil of similar width. A round coil has slightly more depth and sensitivity in non-mineralized soil. Most coils sold for current multi-frequency detectors are Double-D (DD), which Garrett says handles mineralized ground much better than a concentric coil.

Real coil lineups

These are the actual sizes you can buy for common detectors, from the manufacturers’ pages.

Platform Small Medium (often stock) Large
Minelab Equinox 700/900, X-Terra Pro/Elite EQX 06, 6 in round DD, 300 g, $200 to $250 EQX 11, 11 in round DD (stock on Equinox) EQX 15, 15 x 12 in elliptical DD, 660 g, $250 to $300
Minelab X-Terra Elite, Vanquish 560 (VX series) V8X, 8 x 5 in DD V10X, 10 x 7 in DD V12X, 12 x 9 in DD (stock on Elite and 560)
Nokta The Legend LG15, 6 in DD LG24, 9.5 x 6 in DD; LG28, 11 in DD LG30, 12 x 9 in DD (current stock); LG35, 13.5 x 12.5 in DD
Nokta Simplex None listed SX24, 9.5 x 6 in DD; SX28, 11 in DD (stock on Simplex Ultra) SX35, 13.5 x 12.5 in DD
Minelab Manticore M8, 8 x 5.5 in DD M9, 9 in; M11, 11 in DD (stock) M15, 15 x 12 in DD

Weights and prices are Minelab US figures for the EQX coils, and both weights include the protective skid plate supplied with the coil.

Two compatibility points to check:

  • Minelab says the X-Terra Pro and Elite accept both VX and EQX coils. Minelab lists EQX coils for the Equinox models, and says the Manticore works exclusively with its own M-series coils.
  • Minelab’s Amazon listings rate the EQX 06 and EQX 15 to 10 feet on the older Equinox 600/800 and 16 feet on the Equinox 700, 900 and X-Terra Pro. A coil’s water rating can depend on the detector it is attached to.

6 inch vs 11 inch vs 15 inch: the Equinox example

The Equinox family shows the trade-off clearly because all three coils use the same connector:

  • EQX 06 (6 in, 300 g). Minelab describes it as “very sensitive to small targets, and perfect for finding treasure in high trash areas,” and good in difficult terrain. You need more sweeps to cover the same ground. It is included with the Equinox 900. EQX 06 on Amazon, part 3011-0333 .
  • EQX 11 (11 in). The stock Equinox coil. Minelab’s Amazon listing describes it as “a good balance between sensitivity, weight, and ground coverage.” EQX 11 on Amazon .
  • EQX 15 (15 x 12 in, 660 g). Minelab says it provides “maximum depth” for specialized treasure hunting and wide coverage in open spaces. It adds 360 g at the end of the shaft compared with the EQX 06. EQX 15 on Amazon, part 3011-0464 .

The same logic applies if you are weighing an 11-inch coil against a 13 to 13.5 inch one, such as Nokta’s LG28 vs LG35 or SX28 vs SX35. Under Garrett’s classification you move from the top of “medium” into “large.” You gain coverage and depth on bigger targets, but the coil is less precise in clutter and puts more weight out front.

Which size for which ground

Your usual ground Coil to use Why (per manufacturer guidance)
Trashy city parks, tot lots, old home sites, nail-heavy relic sites Small (6 in, or 8 x 5 in) Concentrated field separates good targets from nearby iron and trash
Mixed parks, yards and fields Medium (8 to 11 in, usually the stock coil) Best balance of depth, coverage and target-size range
Open pasture, plowed fields, dry sand with sparse targets Large (12 x 9 in to 15 x 12 in) Fewer sweeps to cover ground; deeper on larger targets
Heavily mineralized soil Medium DD, test before going large Minelab notes larger coils can be more affected by mineralization
Hunting for very small gold or tiny targets Small Garrett and Minelab both tie small coils to small-target sensitivity

If you own one detector and hunt a mix of sites, keep the stock medium coil and add a small coil first if your sites are trashy. Add a large coil only if you regularly hunt open, clean ground. Related reviews: Minelab 6-inch coil , Minelab EQX 15 coil , Garrett Reaper coil and the small coil buying guide .

FAQ

Is a large search coil always deeper?

Generally deeper on larger targets, but not on everything. Garrett’s rule of thumb is that coin-sized detection depth is roughly equal to coil diameter, but it also says very large coils (over about 15 inches) start to miss small objects. Minelab adds that larger coils can be more affected by ground mineralization.

Which coil is better for trashy parks and old home sites?

A small coil. Garrett says a small coil’s concentrated field is the best choice around a lot of metal debris and in tight spots, and Minelab recommends its 6-inch EQX 06 and 8 x 5 inch V8X for high-trash areas.

What counts as a large coil?

Garrett classes coils under 6 inches as small, 6 to 11 inches as medium and over 11 inches as large. An 11-inch round coil, like the Minelab EQX 11, sits at the top of the medium range; a 15 x 12 inch coil like the EQX 15 is large.

Is a 13 or 15 inch coil worth it over an 11 inch?

Only if you regularly hunt open, fairly clean ground and want more coverage per sweep and depth on larger targets. The extra size adds weight at the end of the shaft: Minelab’s EQX 15 weighs 660 g with its skid plate, against 300 g for the EQX 06.

Sources